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From "Chris A. Mattmann (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (SIS-73) Remove the automatic mapping of UUIDs to objects
Date Sat, 08 Jun 2013 04:11:24 GMT

     [ https://issues.apache.org/jira/browse/SIS-73?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chris A. Mattmann resolved SIS-73.
----------------------------------

    Resolution: Fixed
    
> Remove the automatic mapping of UUIDs to objects
> ------------------------------------------------
>
>                 Key: SIS-73
>                 URL: https://issues.apache.org/jira/browse/SIS-73
>             Project: Spatial Information Systems
>          Issue Type: Task
>          Components: Utilities
>            Reporter: Martin Desruisseaux
>            Assignee: Martin Desruisseaux
>            Priority: Minor
>             Fix For: 0.3
>
>
> For every UUID (_Unique Universal Identifier_) assigned to an {{IdentifiedObject}}, SIS
automatically keeps the association using weak references in an internal map. This allow to
retrieve the object by UUID if the object is still alive in the JVM. The rational was that
if UUID are truly unique, then there is few risk of ID clash even if we use a system-wide
map. However this cause a number of risks:
> * The "truly unique" hypothesis may not hold in practice. Consider for example the case
were the user reloads many times the same ISO 19139 document. If the document contains an
object with {{gco:uuid}} attribute, then the same UUID will be assigned many times - admitely
to equivalent objects, but the user could have edited a previously loaded instance.
> * In order to be truly effective, developers need to provide their own "UUID to object"
mapping anyway, because the universe of UUIDs is large and the developers probably have some
database for them. Our own management of "UUID assigned in the current JVM" is likely to overlap
with the developer's database.
> Applying the prudential rule "_in case of doubt, leave it out_", the proposal is to remove
the automatic "UUIDs to objects" mapping, but keep this JIRA task in the archive in order
to make easier to find the Subversion revision number to revert if this functionality is considered
useful in a future SIS version.
> As a minor side effect, the {{putIfAbsent}} method from {{WeakValueHashMap}} should also
be removed. It was added for supporting the feature documented in this JIRA task at the cost
of slight complication of implementation. Given that {{WeakValueHashMap}} is not real concurrent
map, we may be better to avoid any {{ConcurrentMap}} method.

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